In practical engineering systems, permanent magnet synchronous motors (PMSMs) face challenges such as constrained electrical performance output, excessive energy losses, and discontinuous current transitions during condition switching when operating under multi-condition. To address the above problems, this paper proposes a smooth-switching control strategy that combines maximum torque per ampere (MTPA) and loss minimizing control (LMC). This strategy combines the respective advantages of the two control algorithms and can satisfy the demands of different working conditions. In addition, the proposed smooth-switching mechanism effectively eliminates the discontinuous current conversion problem during multi-condition switching, while mitigating the instability and vibration of the system. Then, the current controller is constructed by means of the port-Hamiltonian method. Meanwhile, energy shaping, damping injection and interconnection configuration approaches are introduced to achieve good steady-state performance of the system. Finally, the simulation results verify the effectiveness of the designed strategy.